1. Field of the Invention
This invention relates in general to database management systems performed by computers, and in particular to a method and system for providing conflict detection and resolution in multi-tier client-server communication environments.
2. Description of Related Art
Databases are computerized information storage and retrieval systems. A Relational Database Management System (RDBMS) is a database management system (DBMS) which uses relational techniques for storing and retrieving data. RDBMS software using a Structured Query Language (SQL) interface is well known in the art. The SQL interface has evolved into a standard language for RDBMS software and has been adopted as such by both the American National Standards Organization (ANSI) and the International Standards Organization (ISO).
Lately, with invention of hand-held (client) devices which have a need to communicate with databases on servers, a search for efficient and accurate messaging systems for hand-held devices became important. Some conventional messaging systems only offer message synchronization for two-tier client-server messaging systems. Often, they only allow client-to-server file-to-file synchronization and do not allow message-to-message synchronization, which is much more complicated due to message content and identity options. Sometimes, two-tier messaging systems support only one-way synchronization since they have no server log support and their conflict resolution is in a client-transaction log.
Other conventional messaging systems offer synchronization for three-tier systems which have a client, mid-tier and server, but they have numerous synchronization and replication problems. For example, they cannot detect and handle all cases, they fail to define the cause of a conflict, their server always wins by default, and its action overrides client devices' actions.
Yet other conventional messaging systems offer synchronization in multi-tier client-server environments, which have multiple mid-tiers. However, in those systems a direct synchronization from a tier-0 application (e.g., a calendar application on a hand-held device) to a back-end server (e.g., Lotus Notes or Microsoft Exchange) usually performs poorly due to the computing incompatibility between the limited resources on tier-0 devices and the rich-client synchronization demands from the back-end server. Thus, the most successful conventional n-tier synchronization system synchronizes its tier-0 application with a mid-tier mirror image (a server database backup), instead of the back-end server, to avoid the performance problem. However, this mid-tier mirror image is synchronized or replicated infrequently with the back-end server to exchange the newest delta messages between tier-0 clients (obtained during tier-0 and mirror synchronization) and back-end server data. Moreover, when synchronization systems with mid-tier image synchronization become more complicated, they often fail to detect all possible client/mirror and server/mirror synchronization conflicts and fail to provide complete conflict resolution.
Therefore, there is a need for a simple, optimized and generic method for detection of all possible client/mirror and server/mirror synchronization conflicts which can provide a complete conflict resolution in a multi-tier client-server messaging system.